1. Field of the Invention
The invention relates in general to a method for receiving data and the communication device, and more particularly to a data receiving method capable of saving counter resources and promptly positing the sliding window and a communication device thereof.
2. Description of the Related Art
In a wireless communication system, the packages may be lost or may generate error during data transmission due to the fast change in transmission channels, multiple paths or decay in transmission signals. The automatically repeat request (ARQ) mechanism is one of the technologies for resolving the above problem. The ARQ mechanism uses the acknowledge label value of the acknowledge signal between the transmitter and the receiver to indicate whether a package is received successfully.
If the acknowledge label value of the acknowledge signal transmitted to the transmitter from the receiver is “1”, it is indicated that the corresponding package has been received successfully. If the acknowledge label value of the acknowledge signal transmitted to the transmitter from the receiver is “0”, it is indicated that the corresponding package is missed or received unsuccessfully. The transmitter determines whether to re-transmit corresponding package to the receiver according to the received acknowledge signal.
However, in the conventional ARQ mechanism, after the transmitter transmits a package, the transmitter cannot transmit the next package until the receiver has sent back a acknowledge signal through a feedback channel. As the transmitter waists too much time waiting for the acknowledge signal, the overall transmission efficiency of the wireless communication system is poor. To improve the overall efficiency, another transmitter capable of transmitting multiple packages is thus provided. The receiver corresponding to the transmitter receives the packages by a sliding window, and each package corresponds to a block sequence number (BSN).
After the receiver has successfully received the package, the counter to which the BSN corresponding to the package corresponds is activated for counting. If the counter counts to an up-limited value, then the receiver, according to the ARQ mechanism, will automatically slides the starting position of the sliding window to the position corresponding to the package to be received next, lest the efficiency of the receiver might be affected if a particular package is not received and the receiver has to wait for a long time.
However, the BSNs of the packages used in protocol 802.16d or 802.16e can be as high as 2048. If the abovementioned mechanism of automatic sliding window is used to receive the packages, then 2048 counters will be required, not only largely increasing the cost for the receiver but also occupying too much space of chips due to a large number of counters used. Therefore, how to use the resources of the counters efficiently and promptly and precisely position the starting position of the sliding window so as to achieve a media access control (MAC) layer ARQ mechanism featured by high efficiency, low cost and low chip size has been an imminent issue to be resolved.